Preselective command device



March l, 1966 P, AUDEMAR 3,237,641

PRESELECTIVE COMMAND DEVICE Filed Aug. 29, 1963 4 Sheets-Sheet 1 l FIG.2c:

6 @f "n 38 z l 4(l FIG 3 l |120 72 l 1 so 10k i 52 m so (7s 36l Sf'; 76

PIERRE AUDEMAR March 1, 1965 P. AUDEMAR 393%@ PRESELECTIVE COMMANDDEVICE Filed Aug. 29, 1963 4 Sheets-Sheet 2 FERRE AUDEMAR March 1, 1966P, AUDEMAR 39237,

PREsELEcTIvE COMMAND DEVICE Filed Aug. 29, 1963 y 4 Sheets-Sheet SKEG/108 WERKE AUDEMAR P. AUDEMA 3,23%@

PRESELECTIE COMMAND DEVICE FIG. 7

PIERRE AUDEMAR bj M\ 5W United States Patent 3,237,641 PRESELECTIVECOMMAND DEVICE Pierre Audemar, Paris, France, assignor to SocitAlsacienne de Constructions Mcaniques, Paris,

France, a company of France Filed Aug. 29, 1963, Ser. No. 305,423 Claimspriority, application France, Sept. 19, 1962, 909,826, Patent 1,347,038Claims. (Cl. 137-596.15)

The instant invention concerns a iiuid pressure operated device for thepreselective control or command of an apparatus including a pressureoperated member moving between two limiting positions and moreparticularly preselectively operable means for the later and subsequentcontrol of an hydraulic or pneumatic valve which directly causesoperation of the pressure operated member.

The device according to the invention serves to maintain the valvemember, for example, a valve slide, locked in either of the twopositions it had previously been placed by the preselectively operablecontrol means controlling its movement, so that said preselective meansmay be activated in advance but will only become operative (that is,actually move the Valve member component under command) after the devicehas received a momentary signal causing the unlocking of said valvemember component. A device according to the invention is characterizedin that this signal is in the form of a temporary or momentary lowering,or preferably, a complete cut-oi, of the iiuid pressure in at least thatpart of the pneumatic or hydraulic circuit controlled by the valve(s)preselectively under command.

In a device conforming to the invention for the preselective command ofa two position valve controlling a pressurized fluid circuit, the mobilethrottle component of said valve is mechanically linked to a pistonrunning in a cylinder.

The cylinder is normally in communication with a source of iiuid underpressure, in such a manner as to hold the piston stationary in thecylinder at one or the other of the ends of the course of travel thereofunder the elfect of the pressure exerted on one of the faces of saidpiston, whereby the throttle component of the valve is normally lockedin one or the other of these positions.

f According to the invention, the fluid pressure and thev effectivesurface area of the piston are chosen so that the fluid locking actionwill not be overridden (with the resulting movement of the mobilethrottle component to its other position) by the force exerted on saidcomponent of the valve by the command means, this arrangement allowingsaid command means to be preselectively activated without its having animmediate effect.

The device according to the invention includes as well means fortemporarily reducing or cutting-off the normal pressure exerted by thefluid on the face of the abovementioned piston so as to unlock thethrottle component of the valve and free it to respond to the means ofcommand, if it has been previously activated.

In a preferred embodiment of the invention, the locking piston and thethrottle component, rather than merely being linked together, areactually made an integral part of a piston slide which runs in the bodyof a valve, a part of which body serves as the above-mentioned cylinder.Following this embodiment, one or the other of the 3,237,641 PatentedMar. 1, 1966 lCe faces of the locking piston is normally subject to theiluid pressure prevailing in at least one of the parts of the circuitcontrolled by the valve so that the unlocking of the piston slide maysimply be accomplished by temporarily venting all or part of the abovecircuit to a drain receptacle. The results of this combination aresimple, economical preselective command valves, the invention of coursecontemplating as well the valves themselves.

The preselective valves conforming to the invention find a particularlyinteresting application in the control of gear boxes, as for examplethose found in machine tools or vehicles, with each of the said valvescontrolling the feeding or draining of iuid under pressure of anhydraulic jack which in turn activates the shifter device or analoguousselector device of the gear box. The simultaneous unlocking of all ofthe valves may be realized by opening a single unlock valve whichoperates all of the valves and allows them to respond to what evercommand signals may have been preselectively applied.

The invention will be better understood from a study of the followingdetailed description in Iconjunction with the annexed drawings whichrepresent, by way of example only, certain embodiments of the invention.

On the drawings:

FIGURES 1 and 1a are schematic representations of a preselective controlor command device in accordance with the invention as applied to arotating control Valve.

FIGURES 2 and 2a show a longitudinal cut-away of an embodiment asapplied to a slide valve with electromagnetic command means.

FIGURE 3 is a cut-away view of another variant in construction.

FIGURES 4, 4a and 5 represent another embodiment of a preselective valveaccording to the invention with hydraulic command means, in several ofits operating positions.

FIGURE 6 is an hydraulic schematic representation of the preselectivecommand means of a gear box including automatic command of the couplingsassociated with said box by means of a plurality of valves conforming tothe invention.

FIGURE 7 represents a cross-section of a command block which groups fourpreselecting valves in the same valve body.

FIGURE l illustrates the fact that the invention is applicable to alltypes of valves, be they hydraulic or pneumatic, although the mostadvantageous applications concern those valvesin which the valve membermoves axially. In the following description, the invention will bedescribed as it applies to hydraulic circuits, for purposes ofsimplification, although it is to be understood that it is equallyapplicable to all pressurized fluid circuits.

A rotary three-way valve 2 is shown arranged to con, neet a hydraulicjack 3, either with a pipe 6 carrying fluid under pressure or adischarge pipe S. The valve 2 is mechanically linked to a piston 10 by atransmission system comprising a piston rod 12 provided with a rack 14engaging a pinion (not shown) connected to the valve 2 for rotationtherewith. The Ipiston 10 is slidable in `a cylinder 16 which isnormally in communication with a source (not shown) of pressure fluidthrough a pipe 18-18" through a valve 20, called the unlock valve, whichallows this communication to be momentarily interrupted whileYsimltaneously providing free commnication between the two end chambers36 and 34 at opposite sides of the piston through pipes 22 and 24.

The preselectively operable control means acting on the valve 2 isi'llustratively shown as a manually operable push button 26 linkedthrough a helical spring 28 to a piston rod 30 extending from the piston10.

In the position as shown in FIGURE 1, the jack 4 is under pressure andthe valve 2 remains locked in a position which supplies pressure fluidto the jack due to the fact that the piston is positively held at Ioneend of the cylinder 16 'by pressure uid admitted lthrough the valve 20and the pipes 18, 18'. In order to preselectively actuate valve 2, thebutton 26 is held continuously pressed in the direction indicated 'bythe arrow 32 Ibut the valve is held against operation by the lockingaction of the piston 10, and the sole result of pressing the button 26is the compression of spring 2S. Of course, as already mentioned, thepressure of the fluid admitted into cylinder 16 and the surface area ofthe piston 10 are chosen in such a way as to insure that the hydrauliclocking of the piston 10 will not ybe overcome by the vforce exerted bythe button 26 through the spring 28.

The operation or non-operation of the jack 4 may thus -be preselected atany time lby appropriate positioning of the button 26, which is held inthe preselected position by conventional means (not shown) and thepreselected operation or non-operation will beco-me effective only whenthe locking valve 20 is momentarily rotated 90 to the position shown inFIG. 1a. At that moment, the piston 10 is unlocked, then, due to ttheforce of the compressed spring 28 and/or the force exerted on the button26 it slides freely to the right of the diagram, and the flu-idcontained in chamber 34 of the cylinder is forced to the oppositechamber 36 'by the piston through pipe 24, valve 20 and pipe 22. Thevalve 2 is thus rotated to the position as indicated in FIGURE la andjack 4 drains through pipe 8.

The locking valve 20 can then be returned to its initial position thuslocking the piston 10 in place at the other end of the course of travelthereof and permitting another preselective inverse command of valve 2by pulling on the button 26 in a direction contrary to arrow 32, whichaction will only take effect at the time of the momentary manipulationof locking valve 20.

Of course, it is preferable to employ a pressurized fluid source commonto the device(s) under command 4 and the locking cylinder 16. Thus pipe6 may be joined to pipes 18 and 18.

In the embodiment as represented in FIGURE 2, a locking piston 10sliding in a cylinder 16 is directly coupled, by its rod 12', to theslide 38 of a sliding valve. The cylinder 16', which is closed by ends40 and 42, is the prolongation of the valve body 44 which can be acylinder open at one end.

In the position of the slide 38 as shown in the diagram, the shoulders46, 48 and 50 of said slide put a pressurized oil feed pipe 52 intocommunication with the drain pipe 54 which leads to one of the two endsof a double acting jack 4', which is the apparatus under command. At thesame time, the slide puts a drain pipe 56 into communication with theconduit 58 at the other end of the jack 4.

The two chambers 34 and 36 as delimited in the locking cylinder 16 lbythe piston 10 are connected respectively -by pipes 60 and 62 to pipes 54and 58. As a result, in the position as shown in FIGURE la, theslidepiston combination is kept hydraulically locked to the left end ofthe course of travel by the oil pressure in chamber 34 so that the meansof com-mand may be preselectively activated without their having anyimmediate eifect. By way of example electro-magnetic command means havebeen represented in FIGURE 2 consisting of an armature 64 linked to theslide :by a rod 66 4- controlled by one or "the other of the twosolenoids 68 and 70. All other known means for controlling electrovalvesmay be used.

If the solenoid 70 is preselectively activated, thereby tending to urgethe slide to the right, the pressure applied to the locking piston 10prevents the slide from moving. The operation only becomes effectivewhen the unlock valve 20 is moved to the position shown in FIGURE 2asuch that pipe 52 is linked to drain pipe 72. Chamber 34 is therebydrained through pipes 60-54 and the slide is then `free to move underthe influence of the command means, that is to the right end of thecourse of travel, the piston finally coming to rest against stop 42. Inthis position of the. slide, the shoulders 46- 48 establish a connectionbetween pipes 58 and 52 as well as `between pipes 54 and 56.

As soon as the unlock valve 20 is returned to its initial position(FIGURE 2), the pressurized oil again flows through pipe 52, the centralportion of the valve body, pipe 58 and the right extremity of the jack4' thereby forcing the piston to the left. The oil forced out by thejack piston drains through pipes 54 and 56'. The oil pressure equalizesin chamber 36' through pipe `62 so as to maintain the slide locked inits new position. At this moment, the command means may be de-activated,that is, the solenoid 70 may Ibe de-energized (this operation beingaccomplished manually or automatically) and the valve is then ready topreselectively receive a new order.

FIGURE 3 represents a variant of the embodiment as revealed in FIGURE 2.According to this variant, the locking piston 10' does not function as adouble-acting jack, that is the locking pressure is not alternatelyapplied to rst one piston face and then the other. Rather, to obtain thelocking effect, the pressure is applied to the I exterior face of one orthe other of the end pistons 10 and 50 of slide 38, the body 44 of thevalve, following this variant, being closed at its two extremities byend walls 40 and 74 which determine the two locking chambers 36 and 76.In effect, this modification eliminates the intermediary closure element42 as shown in FIGURE 2 and replaces i-t with a closure element at theextremity of the valve body. It will be observed that chamber 76- inFIG- URE 3 plays the same role as chamber 34 in FIGURE 2 and that it isconnected by pipe 60 (analogous to pipe 60) to conduit 54 which leads tothe apparatus under command (not represented).

The valve command means as indicated in FIGURE 3 are electro-magneticand elastic: a solenoid 70, when energized, tends to urge the armature64, which is fixed to the slide, to the right while a helicalcompression spring 78 tends to urge the slide 38 to the left.

In the position as shown in the diagram, the pressurized fluid admittedthrough pipe 54 from the apparatus under command and into chamber 76 bypipe 60 locks the slide so that solenoid 70- may be preselectivelyenergized but will only operate when the locking valve 20r momentarilydrains the circuit.

In the opposite position of the slide, the fluid pressure in chamber 36locks the valve and holds it stationary against the action of the spring78 which cannot move it to the left until the unlock valve 20 has beenmomentarily activated.

FIGURES 4, 4a and 5 reveal several positions of an alternate embodimentof a preselective command valve: conforming to the invention in whichare combined, in. the interior of the same valve body 44', a hollow,dis-v tributor slide 38", a locking piston 10 and valve command meanswhich are preferably of an hydraulic type, and include a movable piston80 running in a cylinder 82, which cylinder is integral with the valvebody. The distributor slide 38 is, as in the variant as shown in FIG-URE 3, urged to the position represented in FIGURE 4 by a spring 78.

. The preselective command valve controls the flow of pressurized oilinto (FIGURE 4) or out of (FIGURE,

5) chamber 84 of one or several jacks 4 (or other apparatus undercommand), in which jacks the opposing charnber 84' can normally besubject to the oil pressure through pipe 90 (as in the case of adifferential jack piston as shown in FIGURES 4 and 5).

The operation of the device is similar to that of the embodimentsalready described and it is sufficient to mention that in the positionas represented in FIGURE 4, the pressurized fluid preferably oil, flowsfrom its source via pipes 52-52 to the interior of the distributor slide38 through orifices 92 and then to the jack 4 through pipe 86. The drainpipe 94 is closed olf by the cylindrical portion 96 of theslide-distributor and the high pressure found in the body of the valveis applied against the right face of piston in order to maintain theslide locked. The valve may therefore be preselectively commanded byadmitting command pressure into chamber 82 through pipe 98. This commandpressure and the crosssection of the piston face being chosen to insurethat the force exerted to the right be less than the locking force whichis applied in the opposite sense, the slide remains in position untilits unlocking is effected by turning valve momentarily to the positionas shown in FIGURE 4a in which the pressurized lluid feed through pipe52' is temporarily interrupted while pipe 52 is linked to drain pipe 72.The locking pressure on the piston falls as a consequence and thedistributor slide is free to respond to the command means, that is tothe pressure exerted on piston 80. Said piston then moves to theposition as indicated in FIGURE 5 in which the drain pipe 94 is openedand put int-o communication with pipe 86 of the jack 4 through orifices92 and the interior of the slide.

As soon as the unlock valve is returned to its initial position, thepressurized fluid is again admitted into pipes 52-90 and into chamber 84of jack 4 in which piston 88 is forced to the left (FIGURE 5) while thefluid which had been in chamber 84 is drained out through pipe 94.

At the same time, pressure is applied to the left face of piston 10which serves to hold the slide locked in its new position against theaction of spring 78 even when the command pressure is no longer appliedin chamber 82.

The combination of many valves conforming to those already describedadapts particularly Well to the preselective command of 4gear boxescombined, with the command of a clutch which has -been represented inFIG- URES 4 and 5 in dotted lines. A clutch 100 can be activated by ajack 102 supplied with uid by pipe 104 branched onto pipe 52.

While the unlock valve 20' is in its normal position, the clutch isengaged but disengages when valve 20 Iis momentarily turned to theunlock Iposition as shown in FIGURE 4a by draining through pipes 72 and104. The clutch disengages during the intermediate phase of thedistributor slide displacement, that is during the time the gears aredisengaging or engaging, as dictated by the movements of the commandjack 4, and a delay in the clutch action may be introduced if necessary,as follows.

FIGURE 6 is a schematic representation of a hydraulic preselectivecommand circuit conforming to the invention as applied to a three speedgear box 106 in which the chan-ges in ratios are effected by three jacks41-42-43. The three valves 441-442-443-contro11ing the operation ofthese jacks are, for example, of the type as shown in FIGURES 4 and 5and the Ipipes associated with them carry the same reference numbers,with the indices 1-2-3 as in the diagram.

A single unlock valve 20 is connected to the three valves by pipe 52which branches out into three directions 521-522-5211.

The combination is supplied with pressurized oil by a pump 108 whichdraws the oil from a tank 110 and charges an oleo-pneumatic accumulator112. The pressurized oil fed by pipe 114 serves generally to supply thepreselective command means of the valves (pistons 6 and cylinders -82 in(FIGURE 5') through a selector 116 interposed between pipe 118 and thethree pipes 98-98-98, feeding the command pressure to the valves 44. Thedrain pipes 72 and 94 (identical to those indicated in FIGURES 4 and 5)return the oil to the tank 110.

The function of the valves has been suticiently described in connectionwith the preceding embodiments so that it suices to mention that thesole momentary operation of the unlock valve 20 brings labout a changein position in all valves having received a preselective pressure signalopposing the respective position they Occupied at the time and theautomatic return (due to the eifect of spring 78) to the position aslshown in FIG- URE 4 of the valves which have received nopressure signaland which previously occupied the position as indicated in FIGURE 5. Theselector 116 can be disposed in the form of a combiner to control themovements of the gear trains and successively change the gear ratios.The simultaneous operation of clutch is identical to that described inconnection with FIGURES 4 and 5, but an elastic accumulator 120 :and acalibrated throttle 122 are preferably inserted in the circuit to delaythe clutching action during engage and disengage of the gear trains. Ajack 124 controlling a braking device 126 for the gear box may bebranched onto pipe 104 of the clutch jack 102. Normally, the oilpressure in jack 124 holds the brake open but, during the momentarymanipulation of the unlock valve 20', the oil drains thro-ugh pipes 104and 52 thereby freeing the brake which is moved to its braking positionby return spring 128.

FIGURE 7 is a cross-section view of a block of four preselective commandvalves conforming to the invention and capable of controlling, forexample, a four-speed gear box.

Each of the valves may include a hollow, distributor slide 381 38', thewhole central portion of which 101 constitutes the locking piston.

According to their respective positions, the slides connect controlpipes 861, 862, with either the oil feed line 52 or the dra-in pipe 56.In the case indicated in the diagram, the jack controlled by the firstand fourth valves are in the drain position while the jacks controlledby the second and third valves are under pressure.

The control of the valves is accomplished hydraulically, as in FIGURES 4and 5 Where the piston plungers 801, 802-which run in the commandcylinders 821, S22-themselves are fed with pressurized oil by pipes 981,982. The piston rods 1301, 1302 can act on slides 381', 382 simply bypushing aginst them in opposition to the force of springs '781, 782.thus avoiding any problems in centering the slides or piston guides801, 802 Such a valve block may be economically realized in three parts.A principal valve casing fitted with the oil feed 52 and 4drain 56-56lines, an attached piece 134 grouping the command pipes 861, 862

and a control block 136 on which are grouped the hydraulic command means801-821-981, the three parts being assembled in a convenient manner andjoined with oil-tight ring seals such as 13S-140.

Of course, the invention is not limited to the examples described andrepresented and is susceptible to numerous variations accessible to menskilled in the art without departing from the spirit of the invention.

Accordingly, the closing component of the preselective valve followingthe invention may take a form other than the slides shown and may be,for example, a doubleseated valve, a rotating plug, etc.

What is claimed is:

1. A two-position valve, with preselective command, for the control of apressurized fluid circuit, comprising .at least a piston running in acylinder, said piston being mechanically linked to the movable selectorcomponent of said valve, said cylinder being normally in communicationwith a pressurized fluid source which selectively acts on one of thefaces of said piston to hold it in one of the two positions at the endsof its course of travel where said piston locks said movable componentin one of its two positions against the force of command meanscontrolling said movable component, said valve including releasing meansfor freeing said movable component in response to the interruption ofthe above-mentioned communication between the fluid source and the faceof said piston subjected to pressure and for re-establishing thecommunication between said source and the other face of said piston whensaid movable component has changed position un-der the effect of saidcommand means. so as to lock said movable component in its new position.

2. A valve as claimed in claim l wherein the movable selector component`consists of a slide running in a valve casing, said slide being anintegral part of at least a piston sliding in a part of said valvecasing constituting a locking cylinder for said piston.

3. A valve as claimed in claim 2 for the preselective control of the dow:and draining of pressurized lluid to and from at least an apparatusunder command, more especially a jack, wherein the part of the valvecasing constituting a locking cylinder for the above-mentioned piston isnormally in communication with the same pressurized fluid source as thatleading to the apparatus under command.

4. A valve as claimed in claim l, wherein the command means of themovable selector component are electro-magnetic.

5. A valve as claimed in claim 2 wherein the command means of theclosing component are hydraulic or pneumatic, said means including anadditional piston integral with the above-mentioned slide and running inanother part of the valve casing in which the command pressure may bepreselectively established or interrupted.

6. A valve as claimed in claim 5 wherein the abovementioned commandpressure and the effective diameter of the additional piston are suchthat the command force exerted on the slide is less than the lockingforce exerted on said slide.

7. A preselective valve according to claim 1, wherein .theabove-mentioned rele-asing means consist of a three port Valve whichnormally establishes communication between the pressurized fluid sourceand said preselective valve but can selectively connect saidpreselective valve to exhaust to free the selector slide from thelocking action of said pressurized iluid on one of the faces of thelocking piston.

8. A preselective valve according to claim 1, which includes elasticmeans for returning the mov-able selector component to one of its twopositions.

9. A preselective command valve having control over a hydraulicallyactivated apparatus, comprising a piston running in a valve casing, saidpiston being normally `locked in one of two positions by uid pressure onone of its faces, said uid pressure being sufficient to overcome in thesaid pistons initial position, a hydraulic, preselective command signalon the opposite end of said piston; a two-position releasing valve inthe feed line of said fluid which may .be momentarily manipulated so asto cut-off the source of `fluid pressure on the initial locking face ofsaid piston and temporarily vent the chamber associated with said faceto a drain pipe thereby freeing the piston to respond Vto thepreselective command signal; a spring tending to urge the piston back toits original position against the greater hydraulic locking forceexerted on the reverse face of said piston by the fluid pressure whichis newly established in said chamber by returning said two-positionvalve to its initial position, thereby holding said piston in itsalternate position; and a hollow, distributor slide, being theprolongment of said piston, fitted with orilices which, in said slidesinitial position connect said apparatus to said fluid source andconnect, in said slides alternate position, said apparatus to a drainline.

10. A preselective fluid pressure control device comprising: a controlvalve including a control element movable between two limitingpositions; duct means connected to supply pressure uid to said controlvalve, said control valve including means for continuously applying saidpressure uid to said control element to hold said control elementpositively in either of said two limiting positions; utilization meansconnected to said control valve to receive said pressure fluidtherefrom, movement of said control element from one of said limitingpositions to the other selectively controlling the supply of pressurefluid to said utilization means; locking valve means serially includedin said duct means, said locking valve means normally permitting saidpressure fluid to be continuously supplied to said control valve,actuation of said locking valve means interrupting said supply wherebysaid control element is freed to move between said limiting positionsand said supply is shut olf from said utilization means; andpreselective means acting on said control element and selectivelyoperable with said locking valve in its normal position continuously tourge said control element to move from one of said limiting positions tothe other or to cause the same to remain stationary in either of saidlimiting positions, whereby momentary actuation of said locking valvemeans permits said control element to move between said limitingpositions or to remain stationary in accordance with the operation ofsaid preselective means, restoration of said locking valve means to itsnormal position causing said pressure fluid to be re-supplied to saidutilization means in accordance with the preselective operation of saidpreselective means.

11. A preselectively controllable fluid pressure operated devicecomprising: a plurality of Huid pressure operated jacks; a separatecontrol valve connected to supply pressure fluid to each of said jacks,each control valve comprising a control element movable between twolimiting positions; duct means connected to supply pressure fluidsimultaneously to all of said control valves, each control valveincluding means for continuously applying said pressure fluid to itscontrol element to hold said control element positively in either ofsaid two limiting positions, the operation of each jack beingselectively controlled by the position of the control element within thecontrol valve to which it is connected; locking valve means seriallyincluded in said duct means, said locking valve means normallypermitting said pressure uid to be supplied continuously to all of saidcontrol valves, actuation of said locking valve means interrupting saidsupply whereby every control element is freed to move between saidlimiting positions and said supply is shut ofic from all of said jacks;and preselective lmeans operable with said locking valve in its normalposition and acting on said control elements to urge preselected ones ofsaid elements continuously to move from one of said limiting positionsto the other and to cause preselected others of said elements to remainstationary in either of said limiting positions, whereby momentaryactuation of said locking valve means permits said preselected ones ofsaid control elements to move between said limiting positions, saidpreselected others of said elements remaining stationary, restoration ofsaid locking valve means to its normal position causing said vpressurefluid `to be resupplied to said jacks in vaccordance with the operationof said preselective means.

12. A device according to claim 11, further comprising a gear boxcontrolled by said jacks.

13. A device according to claim 11, further comprising: a gear boxcontrolled by said jacks; a clutch connected to said gear box; and fluidpressure operated clutch control means connected to said duct meansintermediate said locking valve means and said control valves, saidclutch control means continuously holding said clutch engaged with saidlocking valve means in its normal position, said clutch being disengagedduring actuation of said locking valve means.

14. A device according to claim 13, further comprising uid owrestricting means interposed between said Clutch control means and saidduct means for delaying re-engagement of said clutch upon restoration ofsaid locking valve means to its normal position.

15. A device according to claim 13, further comprising uid pressureoperated brake means connected to said duct means intermediate saidlocking Vaive means and said control valves, said brake means brakingsaid gear box during disengagement of said clutch.

References Cited by the Examiner UNITED STATES PATENTS M. CARY NELSON,Primary Examiner.

lo HENRY T. KLINKSIEK, Examiner.

1. A TWO-POSITION VALVE, WITH PRESELECTIVE COMMAND, FOR THE CONTROL OF APRESSURIZED FLUID CIRCUIT, COMPRISING AT LEAST A PISTON RUNNING IN ACYLINDER, SAID PISTON BEING MECHANICALLY LINKED TO THE MOVABLE SELECTORCOMPONENT OF SAID VALVE, SAID CYLINDER BEING NORMALLY IN COMMUNICATIONWITH A PRESSURIZED FLUID SOURCE WHICH SELECTIVELY ACTS ON ONE OF THEFACES OF SAID PISTON TO HOLD IT IN ONE OF THE TWO POSITIONS AT THE ENDSOF ITS COURSE OF TRAVEL WHERE SAID PISTON LOCKS SAID MOVABLE COMPONENTIN ONE OF ITS TWO POSITIONS AGAINST THE FORCE OF COMMAND MEANSCONTROLLING SAID MOVABLE COMPONENT, SAID VALVE INCLUDING RELEASING MEANSFOR FREEING SAID MOVABLE COMPONENT IN RESPONSE TO THE INTERRUPTION OFTHE ABOVE-MENTIONED COMMUNICATION BETWEEN SAID SOURCE AND THE OTHER SAIDPISTON SUBJECTED TO PRESSURE AND FOR RE-STABLISHING THE COMMUNICATIONBETWEEN SAID SOURCE AND THE OTHER FACE OF SAID PISTON WHEN SAID MOVABLECOMPONENT HAS CHANGED POSITION UNDER THE EFFECT OF SAID COMMAND MEANS.SO AS TO LOCK SAID MOVABLE COMPONENT IN ITS NEW POSITION.